While there are plenty of dinosaurs that deserve a spot in the game due to uniqueness, appearances in other Jurassic Park/World media, or simply by popular demand, I am only going to stick with what I believe would add the most to the game as of the release of the Carnivore Pack. This would be small herbivores. While small herbivores are now equal in number to small carnivores, small herbivores are more lacking as they only use two rigs, with each dinosaur in both rigs also being fairly similar (but not too similar) to each other. Furthermore, I love using small herbivores as they can be put into small enclosures without seeming in a cramped space as well as to add a sense of scale in mixed herbivore enclosures with larger herbivore species. Unfortunately, with all the large herbivores we have, there are very few small herbivores to use. Furthermore, the three pachycephalosaurs have large social requirements but small social sizes, making it difficult to put them in large mixed enclosures. With that said, here are some suggestions for small herbivores to help them feel more unique:
Small ornithopods/"Hypsilophodontids": Easily one of the most under-represented dinosaurs in all media, these small herbivores are typically used as nothing more than fodder for carnivores which is extremely unfair to them. So I would love to see these herbivores get some representation. Notable examples include:
Dryosaurus
Thescelosaurus
Hypsilophodon (needs to be scaled up)
Heterodontosaurus (would need to be scaled up)
Small ceratopsians: distinguished by their larger relatives by the lack of horns on their head and small body size, having quadrupedal small herbivores would add a whole new body type with a dinosaur group that can potentially fight back against small carnivores.
Koreaceratops (maybe scaled up)
Protoceratops (distinct yet recognizable)
Psitacosaurus (Could certainly have quills like the Indoraptor and Indominus)
Leptoceratops
More pachycephalosaurs and ornithomimids: A couple of suggestions for new dinosaurs in these categories that would be pretty distinct:
Pelecanimimus
Stegoceras (distinct, rounded skull to differenciate it from the other Pachycephalosaurs in the game)
Homalocephale/Stegoceras (former is a juvenile of the latter, but has a more original skull shape, both can be considered)
Misc. herbivores: A variety of ornithischians and saurischians that would fit the small size category.
Oviraptor (while often considered a carnivore, Oviraptorids were more likely herbivorous while Caenagnathids like Anzu were properly omnivorous.)
Scelidosaurus (One of the earliest members of Thyreophora, a lightweight yet armored dinosaur that is completely unique to any other known dinosaur.)
Minmi (a very small bodied ankylosaur and an additional Australian representative, would be unique to have a small bodied ankylosaur that shares the rig of the larger armored herbivores)
Limusaurus/Elaphrosaurus (unique herbivorous theropods more closely related to abelisaurs like Carnotaurus yet having a body plan similar to Ornithomimids and could thus perhaps share their rig. Elaphrosaurus was not preserved with a skull, however recent studies suggest it would have been most closely related to Limusaurus and thus suggested to have been an herbivore. Limusaurus would be the smaller representative while Elaphrosaurus closer in size to Gallimimus.)
Chilesaurus (a bit of an enigma and has been classified as an ornithischian, theropod, and even sauropod in several different papers, this bizarre herbivore would make for an incredibly unique addition to the game)
Massospondylus (while I do think Prosauropods in general need to be represented, I chose Massospondylus due to it being a smaller body size that fits with the other small herbivores currently in the game)
Apologies for the long post, this isn't to be taken as a list of "dinos that MUST be in the game", but rather a list of suggestions, and there are MANY more options than the ones listed here, these are just meant to showcase the untapped potential for small herbivorous dinosaurs that can still potentially see the light of day. Frontier, you have been blowing it out of the park with recent additions, with obscure and popular choices, now give these smol bois some love.